In the hitherto used silver complex diffusion-transfer reversal process, a negative working silver halide emulsion material is image-wise exposed to give a latent image. This exposed material is chemically developed by means of a silver halide developing agent reducing the exposed silver halide, usually in the presence of a silver halide complexing agent for example sodium thiosylfate.
Thereupon the developed material is brought into contact with an image receiving material containing catalytic nuclei for physical development of transferred complexed silver halide.
The transferred complexed non-developed silver halide of the negative material is thereby physically developed on the nuclei by the action of developing agent in alkaline medium to form a silver image. This process is well known in the art.
Tone controlling compounds are used in this process in the image-receiving layers of diffusion transfer receivers to control the tone of the positive image. Many examples are reviewed in the literature for example A. Rott and E. Weyde "Photographic Silver Halide Diffusion Processes", The Focal Press, London and New York 1972, page 61.
Tone controlling compounds can be used on their own or in combination with other toners in the same or adjacent layers.
Conventionally diffusion transfer film receivers have the same layers coated on each side of the base such that identical results are obtained irrespective of which side is laminated with a diffusion transfer donor in a diffusion transfer process.
Two main uses of film receivers of this type require somewhat different properties. Creative design work is best served by a neutral or near neutral image color from the physically developed silver. Further the absence of bronzing is desirable so that the image looks black from whichever side of the film the image is viewed.
However in presensitized plate-making work it is important that the silver image has high blue and UV opacity because the exposing sources in the plate-making step are usually in the UV spectrum; typically "diazo" type lamps with maximum output at 410 nm and "polymer" type lamps with maximum output at 365 nm. If these silver images have high density in the blue and UV it is not necessary for an equivalent density in other parts of the spectrum. Thus red-brown or brown image color may be preferred if it results in high absorption in the blue and UV and low absorption in the red. Also, because in this application the receiver is merely being used as an intermediate it is of little consequence if the image is bronzed.
In U.S. Pat. No. 4,401,753 there is disclosed a photographic material containing a transparent support coated at each side with a negative working hydrophilic colloid silver halide emulsion layer. This arrangement gives a physically developed positive print by diffusion transfer of sufficient density to be used as an internegative.